THE PROBLEM: The lysine-sensitive aspartyl/kinase (AKIII) of E. coli increases in specific activity during log-phase growth, then declines rapidly as the culture enters stationary phase. Previous evidence showed that changes in the quaternary structure and catalytic parameters of the enzyme are associated with this phenomenon. In the next year we plan to grow large cultures, harvest cells at defined points on the growth curve (chosen to maximize the changes in the enzyme) and purify AKIII from those cells. Our object will be to define the change in primary structure which are resposible for the altered physical and catalytic parameters.